You could try another approach entirely.
I'm using a 12 oz Vienna sausage can for a pot/cup. It is about the same circumference as a 25 oz beer can. If you can hold your Heineken can encircled by your fingers, consider using some high temperture (RTV) silcone sealant. I bought some (red) sealer of this type in the automotive section of my local ***Mart and built up two large pads that I can grab between my thumb and two fingers. It is enough to pick up and pour boiling water onto my dehydrated food and good enough to hold a warm drink, once it cools a bit.
For a more flexible beer can pot, you may have more success with the RTV pads added high on the can sides to reduce the heat from your flame reaching them. You may also want to avoid filling it up too high, as the pads do get warm and you will have to grip the can snugly while the sides flex as you pick up the can. A nasty scald is bad enough at home, we sure don't need them in the field.
The pads on my pot have held up for a couple of years, now, so I'm happy with their durability.